President Barack Obama and first lady Michelle Obama wave from the steps of the Lincoln Memorial at the end of a ceremony marking the 50th anniversary of the March on Washington.

President Barack Obama and first lady Michelle Obama wave from the steps of the Lincoln Memorial at the end of a ceremony marking the 50th anniversary of the March on Washington. (Jason Reed / Reuters)

(L-R) President Barack Obama, former President Jimmy Carter, first lady Michelle Obama and former President Bill Clinton wave from the steps of the Lincoln Memorial at the end of a ceremony marking the 50th anniversary of the March on Washington.

(L-R) President Barack Obama, former President Jimmy Carter, first lady Michelle Obama and former President Bill Clinton wave from the steps of the Lincoln Memorial at the end of a ceremony marking the 50th anniversary of the March on Washington. (Jason Reed / Reuters)

In celebration of the 50th anniversary of Martin Luther King Jr.'s "I Have a Dream" speech, President Barack Obama is joined by former President Bill Clinton, dignitaries, celebrities and ordinary citizens to commemorate the events in Washington, D.C.